Dry photopolymer imaging process

ABSTRACT

Copolymers of glycidyl acrylate and allyl glycidyl ether and terpolymers derived from addition of glycidyl methacrylate to the polymerizable mixture, having an inherent viscosity within the range of about 0.09 to 0.28 and an epoxy equivalent of at least about 0.64 per 100 g. of polymer are provided which upon admixture with a catalyst which is a radiation-sensitive aryldiazonium salt of a complex halogenide, provides compositions suitable for use in a dry photopolymer positive imaging process. In the process, the polymer which is non-tacky at room temperature, together with the catalyst is applied to a substrate and exposed to an energy source for example, electromagnetic radiation through a transparency or mask. Following exposure, the coating is heated to the softening point of the unexposed portion of the coating and a powder or toner is applied thereto, the toner being adhered to only the tacky, non-exposed area of the coating, resulting in a pigmented image.

This is a division of application Ser. No. 486,169, filed July 5, 1974,now U.S. Pat. No. 3,997,344 dated Dec. 14, 1976.

BACKGROUND OF THE INVENTION

In U.S. Pat. No. 3,708,296 to Sheldon I. Schlesinger entitled"Photopolymerization of Epoxy Monomers" issued Jan. 2, 1973, there aredisclosed novel compositions comprising various epoxide materials andcertain latent curing catalysts therefor. Such compositions arephotosensitive and when exposed to an energy source such as actinicradiation yield epoxy polymers which are receptive to ink and possessinherent toughness, abrasion resistance, adherence to metal surfaces,resistance to chemical attack, etc. and are thus valuable for manyapplications particularly those involving formation of acid and alkaliresist images for chemical milling, gravure images, offset plates,stencil-making, etc.

Additionally, in copending application Ser. No. 297,829 filed Oct. 16,1972 and commonly assigned herewith, now abandoned, and in U.S. Pat.Nos. 4,054,452, 4,054,451, 4,054,455, 4,054,635 each issued Oct. 18,1977 and 4,056,393 issued Nov. 1, 1977, each being continuation-in-partapplications of divisional applications of said application Ser. No.297,829 certain copolymers of glycidyl methacrylate and allyl glycidylether were found to exhibit improved curing rates, electron sensitivity,photosensitivity and other properties which rendered them especiallysuitable for use in preparation of articles for storing and recordinginformation from laser or electron beam sources or in microfilmpreparation, in the presence of the sensitizers therein described.

It has now been discovered that specific epoxide materials, copolymersof glycidyl acrylate and allyl glycidyl ether, specially prepared, whenutilized with latent curing catalysts, are unique in being tacky at anelevated temperature before light curing and becoming hard and non-tackyupon exposure to light in an imagewise manner. The copolymers also havethe property of being substantially non-tacky at room temperature andhave the ability to imbibe toner or pigment in inverse proportion to theamount of light received. Such properties render the copolymerseminently suitable for use in dry photopolymer imaging processes, i.e.imaging processes which permit elimination of solvents. The ecologicaladvantage of such a process which is devoid of waste-solvent disposal isreadily evident.

Various systems have been heretofore described in which a tackyphotopolymer is exposed imagewise to actinic radiation whereby theexposed areas are crosslinked or polymerized losing their tack afterwhich a dye, pigment or toner is applied to the surface. Only theunexposed areas pick up the colorant because of their tack thus forminga positive reproduction of the image.

Such processes have been used to transfer images from the original andare known commercially as Adherography or Custom Toning. However, noneof the existing systems are without attendant disadvantages. The use ofa system that is tacky at room temperature requires special handling ofthe unexposed film and fixing of the image after development.Conversely, with systems that are non-tacky at room temperature,solvents and other liquids are often necessary to make the substancestacky when tackiness is required. Many of the systems have poor shelflife and require long exposure times or high energy requirements, etc.The majority of such prior systems involve addition-polymerizationreaction mechanisms which have the disadvantageous tendency of absorbingoxygen from the air which acts as a polymerization inhibitor, lowers theradiation-sensitivity of the system and necessitates, in addition tohigh intensity sources of radiation, covering the photopolymer surfacewith a plastic film to protect the tacky coating and to prevent oxygeninhibition.

There is therefore a continued need in the art for dry photopolymerimaging systems which are devoid of the disadvantages enumerated above.

SUMMARY OF THE INVENTION

The present invention provides novel copolymers of glycidyl acrylate andallyl glycidyl ether having pendant epoxy groups, having an inherentviscosity within the range of about 0.09 to 0.28 and an epoxideequivalent of at least about 0.64 derived from a process which comprisesadmixing the respective monomers, in the presence of a polymerizationcatalyst such as benzoyl peroxide, in a solvent which permits reflux ofthe reactants at a temperature below about 90° C.

The invention also provides terpolymers having the same inherentviscosity and expoxide equivalent as described above derived frompolymerization of allyl glycidyl ether, glycidyl acrylate and glycidylmethacrylate.

The invention further provides novel polymerizable compositionscontaining, as latent curing catalysts, aryl diazonium salts of complexhalogenides which are radiation-sensitive and release an active catalystupon exposure to an energy source such as actinic radiation and the useof such compositions in a dry imaging process.

DETAILED DESCRIPTION OF THE INVENTION

Glycidyl Acrylate-Allyl Glycidyl Ether Copolymers and Preparationthereof

The copolymers of the present invention are characterized by having aninherent viscosity within the range of 0.09 to 0.28 preferably 0.15 to0.25 and an epoxide equivalent of at least about 0.64, preferably 0.69to 0.74 epoxide equivalent per 100g. of polymer. These parameters are ofa critical nature since copolymers having either inherent viscositiesoutside of the specified range or epoxy equivalents of less than 0.64are deficient for the purpose of the present invention.

The values of inherent viscosity herein are measured in butyronitrile at25° C unless otherwise indicated. The inherent viscosity is anindication of molecular weight and is determined according to theequation

    η inh = 1n (η.sub.1 /η.sub.0 /C

where C = concentration of copolymer in grams per 100 ml. of solvent and1n (η₁ /η₀) = the natural logarithm of the relative viscosity of thedilute solution.

As is well known in the art, inherent viscosity is an indication ofmolecular weights of polymers. Thus, molecular weights for thecopolymers of this invention having inherent viscosities of about of0.25 are indicated to be about 4200.

The epoxide equivalent and inherent viscosity of the copolymer receivedare selectively controlled by the reaction conditions in terms oftemperature and relative molar proportions of the reacting monomers andcatalysts. In general, copolymers exhibiting the desired viscosity andepoxide equivalent may be obtained when employing molar proportions fromabout 0.9:1 to 7:1 of the glycidyl acrylate to allyl glycidyl ether, thepreferred proportions being within the range of about 1-6 moles ofglycidyl acrylate per mole of allyl glycidyl ether.

The copolymerization is conducted in the presence of a polymerizationcatalyst which is a free radical generator and which facilitatescopolymerization via the double bonds thus rendering a product havingpendant epoxy groups suitable for further polymerization via theradiation-sensitive initiators. Examples of such catalysts includebenzoyl peroxide, azo-bis (isobutyronitrile), p-chlorobenzoyl peroxide,t-butylperoxyoctoate, t-butylperoxy maleic acid, lauroyl peroxide, butylperoxide, etc. of which benzoyl peroxide is the preferred catalyst.Generally, the catalyst is employed in amounts ranging from 0.20 to 0.60mol %, based on the total molar concentration of the monomers and ispreferably from 0.24 to 0.55 mol %.

The reaction may be carried out in various solvents which have boilingpoints below 90° C if refluxing is to be used as the means oftemperature control. But solvents with higher boiling points may be usedif an external temperature control is used. Examples of suitablereaction solvents include methyl ethyl ketone, acetone, dimethyl etherof diethylene glycol, monochlorobenzene, o-chlorotoluene,o-dichloro-toluene, acetonitrile, butyronitrile, etc. and mixturesthereof of which methyl ethyl ketone is preferred.

Copolymers are prepared by admixing the monomers in a solvent containingthe polymerization catalyst after which the reaction mixture is heatedto reflux and maintained at reflux temperature for a period of about 3to 6 hours. The reaction mixture is subsequently allowed to cool to roomtemperature and the copolymer is precipitated from a suitable solventsuch as methanol, ethanol, isopropanol or like compound which is asolvent for the catalyst and unreacted monomers but in which thecopolymer is insoluble. The product is then dried at room temperature.Substantially higher drying temperatures are to be avoided to eliminateundesirable crosslinking, increases in molecular weight orinsolubilization (further polymerization) of the copolymer.

The following examples illustrate typical preparations of copolymers ofthe invention.

EXAMPLE 1

A. Into a 1000 ml. resin flask equipped with a reflux condenser,thermometer, stirrer assembly were placed 81.1g of glycidyl acrylate,13.5g allylglycidyl ether and 0.88g of benzoyl peroxide in 300 ml. ofmethyl ethyl ketone. The reaction solution was heated at reflux withstirring for 51/4 hours at which time it was permitted to cool for 1hour with stirring. 250 ml. of methyl ethyl ketone was then stirred inand the solution was permitted to cool to room temperature overnight.The solution was filtered and added slowly, preferably drop-wise, to 500ml. of vigorously stirred methanol. The thus precipitated white productwas collected and washed thoroughly with methanol after which it wassuction dried at room temperature at gradually reduced pressure down to1.5 mm. There was obtained 66g. of a rubbery, clear copolymer having aninherent viscosity 0.25 in butyronitrile at 25°, Tg=64°, an epoxyequivalent 0.70/100g and an average molecular weight of 4182.

B. The procedure of A above was repeated except that the benzoylperoxide concentration was reduced to 0.44g. There was obtained 68g of acopolymer having an epoxy equivalent of 0.70/100g and an inherentviscosity of 0.17.

EXAMPLE 2

A mixture containing 81.1g glycidyl acrylate, 72g allyl-glycidyl ether,400 ml. methyl ethyl ketone and 1.15g. benzoyl peroxide was heated withstirring at reflux for 51/4 hours employing the apparatus of Example 1.After allowing the clear solution to cool for 1 hour, an additional 400ml. of methyl ethyl ketone was added and it was left to stand overnight.

The solution was then filtered directly into 800 ml. of absoluteethanol. An oily, sticky material settled out on standing. Afterdecanting off the solvent and washing the sticky polymer with methanol,it was dried with a water aspirator vacuum in a cold vacuum oven. It wasfinally dried using the vacuum pump setting down to 2 mm pressure with adry ice trap.

There was obtained 53.0g of a copolymer having an epoxy equivalent of0.67/100g and an inherent viscosity of 0.19.

Glycidyl Acrylate-Allyl Glycidyl Ether-Glycidyl Methacrylate Terpolymersand Preparation thereof

Also applicable in this invention where reduced tackiness (a smallreduction) is desired, is the replacement of a small part of theglycidyl acrylate monomer by glycidyl methacrylate in the free radicalcopolymerization mixture. Thus, while maintaining the allylglycidylether concentration within the appropriate molar proportions set forthhereinabove, for example at 15.7 mole-% of the total monomer mixture,the composition of the remaining polymerizable monomer, in thisinstance, 84.3 mole-%, may be varied to contain up to about 0.25 mole ofglycidyl methacrylate for each mole of glycidyl acrylate, but preferablyup to about 0.15 moles of glycidyl methacrylate per mole of glycidylacrylate. Amounts of glycidyl methacrylate relative to glycidyl acrylatein excess of this act to remove the useful tackiness property asillustrated further hereinbelow.

The terpolymers have the same characteristics of epoxy equivalent andinherent viscosity as set forth above and are prepared by the samemethod. The following example illustrates a typical preparation of aterpolymer of the invention.

EXAMPLE 3

Into a 1000 ml. resin flask equipped with a reflux condenser,thermometer, and stirrer assembly, were placed 22.5g allylglycidyl ether(0.197 mole) 18.8g (0.132 mole) glycidyl methacrylate, 118g (0.921 mole)glycidyl acrylate, 500 ml. methyl ethyl ketone, and 1.46g benzoylperoxide (0.006 mole). The reaction solution was heated under refluxwith stirring for 5 hours, and then allowed to cool to room temperature.An additional 500 ml. of methyl ethyl ketone was then stirred in and theresulting solution was filtered. This filtrate was then added dropwiseto a mixture of 1000 ml. methanol and 1500 ml. isopropanol, withvigorous stirring. The white, gummy precipitate that formed was washedseveral times with fresh isopropanol, and then dried, with the finaldrying under 0.5 mm. of vacuum. There was obtained 91.9g of a pliablepolymer. It had an inherent viscosity = 0.16, and 0.72 epoxyequivalent/100g.

Polymer-Catalyst Compositions and Polymerization thereof in a DryImaging Process

In the description which follows, the term "copolymer" will beunderstood to designate actual copolymers of the invention as well asthe terpolymers which result from incorporation of glycidyl methacrylatein the polymerizing mixture.

In accordance with the present invention, glycidyl acrylate-allylglycidyl ether copolymers or the terpolymers above described are admixedwith a Lewis acid catalyst percursor. The resulting mixture, at aconvenient time subsequently is exposed to irradiation, for example,electromagnetic or electron beam irradiation, to release the Lewis Acidcatalyst in sufficient amounts to initiate the desired polymerizationreaction and used in a dry photoimaging process as described hereinbelow.

The materials utilized as latent polymerization initiators in theprocess and compositions of the present invention areradiation-sensitive catalyst precursor which decompose to effectpolymerization upon application of energy. The energy required foreffective decomposition may be energy applied by bombardment withcharged particles, notably by electron beam irradiation. Preferably,however, the catalyst precursors are photosensitive and the requiredenergy is imparted by electromagnetic irradiation and especially actinicirradiation which is most effective at those regions of theelectromagnetic spectrum at which there is high absorption ofelectromagnetic energy by the particular catalyst precursor used. Morethan one of these types of energy may be applied to the system, e.g.ultra-violet light irradiation followed by electron beam irradiation. Itis a unique feature of the copolymers of the invention that irradiationalone without subsequent heating is sufficient to effect a rapid andsatisfactory cure.

The radiation-sensitive Lewis acid catalyst precursors are aromaticdiazonium salts of complex halogenides which decompose upon applicationof energy to release a halide Lewis Acid as disclosed in U.S. Pat. No.3,708,296 and may be prepared using procedures known in the art asdisclosed therein, said disclosure being incorporated herein by theaforegoing reference. The aromatic diazonium cation may be representedgenerally as (Ar--N.tbd.N)⁺, where the aryl group Ar, which may be analkaryl hydrocarbon group, is bonded to the diazonium group by replacingone of the hydrogen atoms on a carbon atom of the aromatic nucleus, andwhere the aryl group ordinarily carries at least one pendant substituentfor greater stability of the cation. Thus the pendant substituent may bealkyl, or another substituent, or both. The complex halogenide anion maybe represented by (MX_(n+m))^(-m). Thus, the photosensitive salt and itsdecomposition upon actinic irradiation may be depicted as follows:

    [Ar--N.tbd.N].sub.m.sup.+ [MX.sub.n+m ].sup.-m hv mAr--X+mN.sub.2 +MX.sub.n (I)

where X is the halogen ligand of the complex halogenide, M is themetallic or metalloid central atom thereof, m is the net charge on thecomplex halogenide ion, and n is the oxidation state of M and the numberof halogen atoms in the halide Lewis acid compound released. The Lewisacid halide MX_(n) is an electron pair acceptor such as FeCl₃, SnCl₄,PF₅, AsF₅, SbF₅, BiCl₃, and BF₃ which upon suitable irradiation of thediazonium complex salt is released in substantial quantities andinitiates or catalyzes the polymerization process, wherein the polymericmaterial is polymerized or cured as the result of the actinicirradiation.

Illustrative of the aromatic diazonium cations comprised in thephotosensitive catalyst salts utilized in accordance with the presentinvention are the following:

p-chlorobenzenediazonium

2,4-dichlorobenzenediazonium

2,5-dichlorobenzenediazonium

2,4,6-trichlorobenzenediazonium

2,4,6-tribromobenzenediazonium

o-nitrobenzenediazonium

p-nitrobenzenediazonium

4-nitro-o-toluenediazonium (2-methyl-4-nitrobenzenediazonium)

2-nitro-p-toluenediazonium (4-methyl-2-nitrobenzenediazonium)

6-nitro-2,4-xylenediazonium 2,4-dimethyl-6-nitrobenzenediazonium)

2-chloro-4-(dimethylamino)-5-methoxybenzenediazonium

4-chloro-2,5-dimethoxybenzenediazonium

2,4',5-triethoxy-4-biphenyldiazonium(2,5-diethoxy-4-(p-tolyl)benzenediazonium)

2,5-diethoxy-4-(phenylthio)benzenediazonium

2,5-diethoxy-4-(p-tolylthio)benzenediazonium

p-morpholinobenzenediazonium

2,5-dichloro-4-morpholinobenzenediazonium

2,5-dimethoxy-4-morpholinobenzenediazonium

4-(dimethylamino)-1-naphthalenediazonium

Illustrative of the complex halogenide anions comprised in thephotosensitive catalyst salts utilized in accordance with the presentinvention are the following:

tetrachloroferrate(III), FeCl₄ ⁻

hexachlorostannate(IV), SnCl₆ ²⁻

tetrafluoroborate, BF₄ ⁻

hexafluorophosphate, PF₆ ⁻

hexafluoroarsenate(V), AsF₆ ⁻

hexafluoroantimonate(V), SbF₆ ⁻

hexachloroantimonate(V), SbCl₆ ⁻

pentachlorobismuthate(III, BiCl₅ ²⁻

A selection of aromatic diazonium salts of complex halogenides is listedin Table I of the aforementioned U.S. Pat. Nos. 3,708,296 and 3,794,576issued Feb. 26, 1974, such disclosures being incorporated herein byreference thereto.

Referring to equation I hereinabove showing the photolytic decompositionof the catalyst precursor, the halide Lewis acid MX_(n) released reactswith the epoxide material with a result exemplified by the following:

    (ArN.sub.2).sub.m (MX.sub.n+m) + copolymer .sup.radiation polymer. (II)

the cationic catalyst is believed to act by cleaving a carbon-oxygenepoxy bond, initiating growth of a polymeric chain or permittingformation of a cross-linkage. A general application of the processembodied by equations I and II as used in the dry photoimaging processherein can be as follows: a diazonium complex salt, for example, asidentified hereinabove, is admixed, with the use of a suitable solvent,with the epoxy copolymer. The mixture is thereafter coated on a suitablesubstrate such as a metal plate, rubber, wire screen, ceramic, glass,plastic, or paper, and the substrate is exposed imagewise to an energysource, for example, actinic radiation. The orginal image source to berecorded may be a photographic transparency with a halftone orcontinuous tone image, alphanumeric information, line-drawing or anyother type of image. It may also be an image which is projected by meansof actinic radiation or scanned by means of a laser or electron beam. Onexposure, the diazonium compound decomposes to yield the Lewis acidcatalyst, which initiates the polymerization and hardening of the epoxycopolymer in the exposed areas.

After exposure, the coating is heated to the softening point of theunexposed coating, about 55° to 75° C, and a toner powder is applied tothe surface by any convenient means as by brush, fluidized bed, spray,etc. The excess colorant powder not adsorbed or attached to the surfaceis then removed therefrom in any convenient way, for example byemploying a vacuum, vibration, air blowing, brush or absorbent pad, etc.An image results with optical density in direct proportion to that ofthe original image. The system reproduces positive from positive ornegative from negative, i.e. the more exposed the area is, the lesscolor it will pick up. The copy may then be re-exposed to the energysource to fade away the yellow color in the background which may bepresent due to unphotolyzed photoinitiator. This step, together with afinal heating step, if desired, may be employed to stabilize the imageand fuse the toner in place although such steps are not necessary inmost cases. In a preferred embodiment, the toner is specially selectedto convey specific properties to the coated substrate as will beillustrated further hereinbelow.

The source of radiation for carrying out the method of the presentinvention can be any suitable source, such as the actinic radiationproduced from a mercury, xenon, or carbon arc, a beam from a lasersource, for example a He--Cd laser, or the electron beam produced in orfrom a cathode ray gun. The only limitation placed on the radiationsource used is that it must have an energy level at the irradiated filmsufficient to impart to the polymerizable system energy at an intensityhigh enough to reach the decomposition level of the photosensitivecompounds. As previously noted, the wavelength (frequency) range ofactinic radiation is chosen to obtain sufficient absorption of energy toexcite the desired decomposition.

The procedures for mixing the radiation-sensitive compositions of thepresent invention using the copolymeric epoxide are relatively simple.The epoxide is combined with the catalyst precursor in a suitable inertvolatile solvent. By such a suitable solvent is meant any solventcompound or mixture which boils below about 190° C and which does notreact appreciably with the epoxide or the catalyst precursor. Examplesof such solvents include acetone, methyl ethyl ketone, dimethyl ether ofdiethylene glycol (bis(2-methoxyethyl ether), monochlorobenzene,o-chlorotoluene, o-dichlorotoluene, acetonitrile, butyronitrile,cyclohexanone, tetrahydrofuran or mixtures thereof and also mixtures ofthese solvents with other compounds in which the copolymer issubstantially insoluble such as toluene, ethyl ether, anisole,1,1,2,2-tetrachloroethane and trichloroethylene.

The amount of catalyst precursor employed should be sufficient to insurecomplete polymerization. It has been found that quite satisfactoryresults are obtained by providing a diazonium complex salt in amount byweight from about 0.5% to about 5% of the catalyst precursor relative tothe weight of the polymerizable material provided, about 1% or less ofthe precursor being amply effective.

Various materials may be employed as toners or pigments herein providedthat the powdered material is dry and non-tacky under the processingconditions employed in the imaging process. It is possible according tothe invention to selectively apply specific toners or pigments to conveyspecific properties to the coated substrate. For example, materials witheither ink attracting or ink repelling properties may be selectivelyapplied. Such materials adhere only to the unexposed areas of the coatedsubstrate forming a coating over these areas in an imagewise manner toimpart specific properties, as desired, without affecting the exposed ornon-imaged area.

Thus, in the use of the invention for the manufacture of printingplates, for example, a hydrophilic powdered material may be employed torender the original image areas oleophobic when the plate is first wetwith water. Similarly, it is possible to apply an oleophobic substanceto render the image oleophobic without using water or to apply anoleophilic material to enhance the oily-ink receptivity of the originalimage areas.

Suitable powdered materials that may be applied to create oleophobicareas include Teflon, poly(tetrafluoromethylene), silicone releaseagents such as Dow-Corning, Syl-off 23, Syl-off 291, c4-2114, orc4-2125, etc. (See A. E. Bey, Adhesives Age, October, 1972, p. 29-30 fora description of typical silicone release agents.)

Examples of powdered materials that may be applied to create hydrophilicareas include polyacrylamide, alumina, aluminum, natural and syntheticpolyhydroxylated polymers such as polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, etc.

Oleophilic substances suitable for use include p-phenylenediaminesilica, azobisformamide, etc.

Various dyes, pigments and color-forming components are also suitablefor use as the toner herein. Among the dyes and pigments useful in theinvention are commercially available powders such as Lumigraphic ROrange (Imperial Dye Co.); Graphtol Green, Acetosol Blue, Acetosol BlueRLS (CI Solvent Blue 45), Acetosol Fire Red 3 GLS (Sandoz Products,Ltd); Irgasol Black RL, Irgasol Blue 2 GLN, Orasol Brown GR, OrasolBlack 2RG (CI Solvent Black 2) (Ciba-Geigy); Yellow Toner CAT. #22-144;914 Copier Toner (Xerox Corp.); BLK 4LOT4; BLK 2 LOT 8 (E. I. Dupont)FW2-4 toner, HB5-18, FW2-40A (Nashua Corp.); powdered carbon, graphite,talcum, titanium dioxide, phosphor particles, ceramics, clays, metalpowders such as aluminum, silver, copper, iron, bronze, etc. and theiroxides and various mixtures and combinations of any of these. The use ofconductive metal powders applied in a predetermined pattern to createdistinct conductive paths on the surface may be applied to theproduction of electronic circuits as on a printed circuit board and areparticularly useful herein. Additionally, certain metal oxides may beemployed to convey magnetic properties to the substrate.

Particle sizes of the developing powders or toners useful in thisinvention are not critical and may vary as desired. In general, thetoners have particles of sizes from about 0.2 to about 40 microns,preferably 0.2 to 1 micrometers (um).

Similarly, thicknesses of the coating layer applied to the substrate mayvary, generally within the range of about 0.2 to 50, preferably 0.2 to20 micrometers.

If desired, in yet another embodiment of the invention, the tackiness ofthe unexposed coating may be enhanced by use of mixtures of liquidepoxides with the copolymers of the invention as illustratedhereinbelow. Such epoxides include liquid epoxides, such ascycloaliphatics for example bis(cycloalkyl) esters and ethers, lowmolecular weight bis-phenol A glycidyl ether, polyglycidyl ethers ofpolyhydric alcohols, polyglycol diepoxides, etc.

In summary, the imaging process of the invention comprises admixing thecopolymer with a suitable aromatic diazonium salt of a complexhalogenide, applying said mixture to a substrate, and exposing thecoated substrate to irradiation through a transparency or a mask orother material having opaque portions. Following exposure, softening ofthe unexposed area of the coating is effected, preferably by heatingfrom about 55° C to about 75° C, and the developing powder or toner isapplied to the tacky, unexposed area of the coating, resulting in animage with optical density in direct proportion to that of the originalimage.

In somewhat greater detail, the toner is applied to the coating whilethe unexposed powder receptive areas thereof are in a softened, tackycondition and the coating is at a temperature below the melting point ofthe exposed, cured copolymer and of the powder. The powder isdistributed over the area to be developed and becomes adhered or imbibedtherein. After the powder application, excess powder is removed bysuitable means, as by a blower or wiping with a pad or brush or vacuum,etc.

The instant dry imaging system employing the copolymer of the inventionis characterized by utilizing a coating which is tack-free at roomtemperature so that it can be stacked or rolled prior to processing.Additionally, contact prints may be made without moving the surface.With prior procedures utilizing coatings that are tacky at roomtemperature, this is not possible unless a protective cover is used suchas a sheet of plastic film. The imaging system of this invention is notinhibited by atmospheric oxygen and therefore eliminates the need forprotective plastic film coverings employed heretofore for this purpose.The system reproduces positive from positive or negative from negative,i.e., the more exposed an area is, the less color it will pick up. Ifdesired, the developed image may be re-exposed to irradiation to fadeaway yellow background color which may be present as a result ofunphotolyzed photoinitiator. This step plus a final heating step, ifdesired, will serve to stabilize the image and further fuse the toner inplace. It will be understood that such additional steps are optional andare not necessary for the successful operation of the invention.

The imaging system of the invention is eminently suitable for use incomputer printouts, package printing, office photocopying, contactphotographic prints, photographic imaging in general; laser recording,electron beam recording, transfer processes, plateless printing, printedcircuits, etc.

The following examples will serve to further illustrate the process ofthe present invention.

EXAMPLE 4

A solution containing 9g of the glycidylacrylateallyl glycidyl ethercopolymer of Example 1A, 75.9g butyronitrile, 15.2g o-chlorotoluene, and0.45g 2,5-diethoxy-4-(p-tolylthio) benzene diazonium hexafluorophosphatewas whirl-coated onto aluminum plate and onto Mylar film (a commerciallyavailable polyethylene terephthalate film), respectively, at 60 rpm.

Samples of the coatings were exposed for 1/2 to 1 second at 22cm.distance from a 360 Watt Gates Raymaster Uviarc lamp through variousphotographic transparencies consisting of line-drawings and continuoustone images.

Following exposure, the samples were heated for 5 to 15 seconds at60°-70° C under an infrared heat lamp. After removal of the lamp, Xerox914 copier toner was dusted on and brushed off using a pad of absorbentcotton. The result was a black positive reproduction of the originalimage. Microfilm images were also copied with resolution to about 50line-pairs/mm.

EXAMPLE 5

The procedure of Example 4 was repeated employing the same formulationexcept that the following dyes or pigments were substituted for theXerox toner:

Lumigraphic R Orange

Acetosol Green BLS

Acetosol Fire Red

Graphtol Green

Acetosol Blue RLS

following exposure and development as in Example 4, all of the abovedyes or pigments gave images varying in resolution and reaching 100line-pairs/mm in several cases. The sharpest resolution in this serieswas obtained with Acetosol blue RLS which also gave a good copy of acontinuous tone positive transparency.

EXAMPLE 6

The procedure of Example 4 was repeated employing the same formulationtherein. However, the transparencies were positive microfilm on 35mmframes (to 50 line-pairs/mm resolution) and on microfiche (to 100line-pairs/mm). The pigments employed were Orasol black, Orasol brownGR, Irgasol black RL and Irgasol blue 2 GLN. Even the smallest lettersof the 35mm format were resolved with Orasol brown, Irgasol black andOrasol black while with Irgasol blue only the larger letters wereresolved. With Orasol black even the smallest letters (100line-pairs/mm) of the microfiche format were resolved while Orasol brownand Irgasol black resolved only larger letters on this format.

EXAMPLE 7

The following formulation was prepared with the addition of liquid epoxyERL 4234, a cycloaliphatic epoxide,2-(3,4-epoxycyclohexyl-5-5-spiro-(3,4-epoxy) cyclohexane-m-dioxaneavailable commercially from Union Carbide, to enhance the tackiness ofthe unexposed coating and therefore the toner takeup of the coating:

7g of the copolymer of Example 1A

2g ERL 4234

75.9g butyronitrile

15.1g o-chlorotoluene

0.450g 2,5-diethoxy-4-(p-tolylthio)benzene diazonium hexafluorophosphate

Whirl coatings were made on Redicote brush-grain aluminum as in Example3. Samples of coated aluminum were exposed through photographictransparency images of a continuous tone positive, a microfiche negativeand 35mm copies of fine print and line-drawings. Exposure was about 1/2to 1 second at 22cm from a 360 Watt Uviarc lamp. After exposure, eachsample was heated for about 10 seconds at 60° C. Then each sample wasdusted over with Xerox 914 copier toner. In each case an excellentpositive black copy of the original image was achieved. Exposure of aKodak No. 2 step tablet with 21 steps of optical density from 0.05 to3.5 for 3 seconds resulted in a copy, after processing, with eithercompletely colorless steps or shades of gray corresponding to the first12 steps of the tablet. Other images were made using Acetosol blue andDuPont Toner BLK 4 LOT 4, both of which were rated as excellent.

EXAMPLE 8

A formulation containing 8g of the copolymer of Example 1B, 67.5gbutyronitrile, 13.5g o-chlorotoluene and 0.40g2,5-diethoxy-4-(p-tolylthio) benzene diazonium hexafluorophosphate waswhirl-coated on aluminum, exposed and processed as in Example 7employing DuPont Toner BLK 4 LOT 4. A good reproduction of line drawingsand printed matter was obtained.

EXAMPLE 9

A formulation containing 9g of the copolymer of Example 2, 75.9gbutyronitrile, 15.1g o-chlorotoluene and 0.450g of2,5-diethoxy-4-(p-tolylthio) benzene diazonium hexafluorophosphate waswhirl-coated on aluminum and exposed and processed as in Example 6employing DuPont Toner BLK 4 LOT 4. In addition to a good line drawing,alpha-numeric information on 35mm film and a continuous tone photographwere copied successfully.

EXAMPLE 10

A. A solution was prepared consisting of 18g. of the copolymer ofExample 1A, 151.8g butyronitrile, 30.2g o-chlorotoluene and 0.90g of2,5-diethoxy-4-(p-tolylthio) benzene diazonium hexafluorophosphate. Thesolution was used to make coatings at 60 rpm on brush grained aluminumlitho plate samples.

B. Coated plates were exposed for 1 second through a positive bar charttransparency image to a 360W Uviarc lamp at 22 cm distance. The plateswere then heated at 60°-70° C for 5 to 15 seconds under an infraredlamp. Immediately after removal from the lamp and while still hot, theplates were dusted over with silica and p-phenylenediamine hydrochloriderespectively. When the plate had cooled to room temperature, the excesspowder was wiped off with absorbent cotton. In each case the powderremained only on the unexposed areas corresponding to the black lines ofthe original image.

The thus obtained imaged plates were heated for 11/2 hours at 165°-170°C after which they were rubbed over with Lithographic Black Process Ink(M&T Chemicals) and wiped dry with absorbent cotton. In each case, theink was taken up only in the image areas which had been coated with thepowdered toner indicating production of a positive-working printingplate.

EXAMPLE 11

The procedure of Example 10 was followed for two different plates up tothe preparation for application of powder. In this example, the powdersused were Elvanol (polvinyl alcohol) and alumina, respectively. Eachpowder-imaged plate was then heated for 3 minutes at 165°-170° C. Beforeapplying ink, they were wet with water which adhered to the image areasonly. When the ink of Example 10 was applied, it was taken up by allareas of the plate but preferentially in the non-image area (originallyexposed area) which will become the image-printing area because of itsink-receptivity. This is, therefore, a negative-working plate.

EXAMPLE 12

The procedure of Example 10 was repeated except that Teflon powder wasemployed as the developing material. The toner adhered only to theunexposed area corresponding to the original image. The Teflon-developedplate was given an overall exposure to ultraviolet radiation for 2minutes to complete the curing of the image areas. When inked, anegative-working plate was obtained since the ink was selectively takenup only by the non-image areas which were free of Teflon.

EXAMPLE 13

The powder of Example 10 was replaced by azobisformamide, an organicfoaming agent available commercially as Cellogen AZ (Uniroyal ChemicalDivision, Naugatuck Chemicals, Inc). After formation of the powderimage, the plate was heated for 11/2 hours at 165°-170° C. When inkedwith Red Developer ink (Minnesota Mining and Manufacturing Company), theink was taken up only by the image areas bearing the Cellogen AZ toner.It was found that the image elements could be raised or expanded byheating the plate to 190°-200° C for 5 minutes prior to inking thusforming a relief image.

EXAMPLE 14A

A 15% solution of the copolymer of Example 3 in a 6:1 solution ofbutyronitrile and o-chlorotoluene was containing 5% of the resin weightof 2,5-diethoxy-4-(p-tolylthio) benezene diazonium hexafluorophosphatewas spin coated onto Cronar at rpm spinner speed. After drying, acontact copy of a 24X reduction microfiche was made by 10 secondsexposure to a 125W Aristo Grid Lamp with maximum output between 365 and420 nm. The exposed film was put through the hot rollers of a Kalvar DryDeveloper machine, set at 130° C for 2 passes, each pass being of a fewseconds duration. While still hot, the film was dusted with Nashua Corp.toner No. FW2-40A. After brushing off the excess toner, a sharp,positive copy of the original microfiche information was obtained, butnot as dark as a similarly processed coating made with the copolymer ofExample 1A.

The method of heating the exposed coating in this example does not implythat a surface temperature of 130° C was required. It was found, howeverthat the Kalvar Dry Developer machine was a good device for rapidlyraising the surface temperature to about 60° C during the rapid movementof the sample through the hot roller-conveyor belt system of thismachine.

EXAMPLE 14B

Into a 2000 milliliter resin flask was placed 22.5 grams of allylglycidyl ether (0.197 moles), 101.3 grams of glycidyl acrylate (0.792moles) and 37.5 grams of glycidyl methacrylate (0.264 moles). Also addedto the reaction mixture was 500 mls. of methyl ethyl ketone as solventand 1.46 grams of benzoyl peroxide as the initiator. The flask wasprovided with a ground glass stirrer assembly reflux condenser andthermometer. The mixture was stirred vigorously while heating at refluxfor 5 hrs., then left to cool to room temperature without stirring. Thereaction solution was slowly added to rapidly stirred 1500 millilitersof methanol in a beaker. A sticky white residue formed. It was washedwith methanol and transferred to a Teflon-lined baking pan for drying.Drying was done at room temperature and atmospheric pressure and finallydown to a vacuum of 20 psi. The very final drying was done at 0.5 mmpressure. 108 grams of a rubbery solid was obtained which was drier andnot as elastic as the copolymer prepared in Example 3. The terpolymerhad an inherent viscosity of 0.20 and epoxy equivalent/100 grams equalto 0.74. A 15% solution of this polymer was made up in a 6:1butyronitrile-o-chlorotoluene solvent mixture similar to that used inExample 14A, also containing an amount of 2,5-diethoxy-4-(p-tolylthio)benzene hexafluorophosphate catalyst equivalent to 5% of the resinweight. Coatings were prepared and dried and then exposed imagewise asin Example 14A. When the coating was heated and toner applied as inExample 14A, it had little or no toner receptivity since the polymer hadlittle or no tackiness on its surface.

It will be seen from Examples 14A and B that terpolymers of allylglycidyl ether, glycidyl acrylate and glycidyl methacrylate areeffective for use in the dry photopolymer imaging process of thisinvention as long as the glycidyl methacrylate is employed in amountsthat do not exceed about 0.25 mole per mole of glycidyl acrylate presentin the polymerizable monomer mixture. As shown in Example 14B, amountsin excess of this proportion act to remove the useful tackiness propertyresulting in little or no toner receptivity.

While the process has been described hereinabove as primarily an imagingprocess, it should be understood that the compositions of the inventionare also suitable for use as coatings and particularly in instanceswhere it may be desired to prepare a surface for future receptiveness ofcolor or other uses to which toners may be put. In such a process,portions of the coated substrate are not screened from irradiation asdescribed hereinabove. The copolymer or terpolymer together withcatalyst therefor is coated on a suitable substrate such as, forexample, aluminum, plastic, or any of the substrates identifiedhereinabove, and dried. Being non-tacky at room temperature, the coatedsubstrate may be readily stored until use is desired at which time, thecoated substrate is heated to soften its surface, in general at 55° C toabout 75° C, toner is applied and imbibed therein after which the thustreated surface is exposed to irradiation without screening to provide acolored, cured, solvent-insoluble coated substrate.

While there have been described particular embodiments of the invention,including those at present considered to be the preferred embodiments,it will be obvious to those skilled in the art that various changes andmodifications may be made therein without departing from the invention,and it is aimed, therefore, to cover in the appended claims all suchchanges and modifications as fall within the true spirit and scope ofthe invention.

We claim:
 1. A composition of matter comprising, in admixture, a polymerselected from the group consisting of (a) copolymers of glycidylacrylate and allyl glycidyl ether and (b) terpolymers of glycidylacrylate, glycidyl methacrylate and allyl glycidyl ether containing upto about 0.25 mole of glycidyl methacrylate per mole of glycidylacrylate, said copolymers and terpolymers having an inherent viscosityof from about 0.09 to 0.28 and an epoxide equivalent of at least about0.64 per 100g. of polymer and, as a latent curing catalyst, an aromaticdiazonium salt of a complex halogenide which decomposes upon exposure toirradiation to release a Lewis Acid effective to initiate polymerizationof said copolymers and terpolymers, said diazonium salt having theformula

    (ArN.sub.2).sub.m.sup.+ (MX.sub.n+m).sup.-m

wherein Ar is an aryl group, X is halogen, M is As, Sb, Bi, Fe, Sn, P orB, n is the oxidation state of M and m is the number of diazonium groupsin the diazonium salt as determined by the net charge on the complexanion.
 2. A composition of matter as claimed in claim 1 wherein theanion of said aromatic diazonium salt is a hexafluorophosphate.
 3. Acomposition of matter as claimed in claim 2 wherein said diazonium saltis 2,5-diethoxy-4-(p-tolylthio)benzene diazonium hexafluorophosphate. 4.A composition of matter as claimed in claim 1 wherein said polymer is acopolymer of glycidyl acrylate and allyl glycidyl ether.
 5. Acomposition of matter as claimed in claim 4 wherein the inherentviscosity of said copolymer is between about 0.19 and about 0.25.
 6. Acomposition of matter as claimed in claim 5 wherein the epoxideequivalent of said copolymer is between about 0.69 and 0.75 per 100g. ofpolymer.
 7. A composition of matter as claimed in claim 1 wherein saidpolymer is a terpolymer of glycidyl acrylate, glycidyl methacrylate andallyl glycidyl ether.